Cooling device

ABSTRACT

A cooling device to which a heating element is joinable includes a base, a plurality of first groups of pin fins and a plurality of second groups of pin fins. The second groups and the first groups are arranged alternately in a flow direction in which a cooling medium flows through a passage of the base. A second outermost pin fin of each second group is more distant from a side surface of the base than a first outermost pin fin of each first group. Width between a side surface of the second outermost pin fin of each second group and the side surface of the base is the same as or larger than width between a side surface of the pin fin of each first group that is adjacent to the first outermost pin fin of the first group and the side surface of the second outermost pin fin.

BACKGROUND OF THE INVENTION

The present invention relates to a cooling device that cools a heating element that is joined to a base via a cooling medium that flows through a passage of the base.

Japanese Unexamined Patent Application Publication No. 2012-29539 discloses a cooling device having a base on which a heating element such as an electronic component is mounted from outside and in which a passage is formed to allow a cooling medium to flow therethrough for cooling the heating element.

In the cooling device disclosed by the above Publication, a plurality of pin fins are provided in a staggered arrangement in the passage of the base for increasing the area of contact between the inner surface of the passage and cooling medium. Transferring the heat radiated from the heating element to the base, the pin fins promote heat radiation from the inner surface of the passage to the cooling medium thereby to cool the heating element efficiently.

The cooling device disclosed by the above Publication has a passage control unit between the pin fins and the inner side surface of the passage that extends along flow direction of the cooling medium in the passage. The passage control unit guides the cooling medium flowing through the passage away from the inner side surface of the passage so that the cooling medium flows toward the region of the base in which the pin fins are formed. Therefore, the cooling medium is prevented from flowing through the gap between the inner side surface of the passage and the pin fins without flowing through the region of the base, with the results that the heating element is cooled further efficiently.

In the above-described cooling device wherein the passage control unit is disposed in the passage of the base, a space needs to be ensured in the passage for the passage control unit, which makes the base larger.

In the cooling device, the provision of the passage control unit reduces the sectional area of the passage of the base thereby to reduce the gap between the passage control unit and the pin fins, so that a pressure loss occurring when the cooling medium flows through the passage is increased, which makes it difficult for the cooling medium to flow through the passage smoothly.

The present invention is directed to providing a cooling device that is reduced in size and allows a smooth flow of a cooling medium.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, there is provided a cooling device to which a heating element is joinable. The cooling device includes a base, a plurality of first groups of pin fins and a plurality of second groups of pin fins. The base has a passage through which a cooling medium flows. The first groups of pin fins are located in the passage and adjacent to the heating element. The pin fins of each first group are arranged in a width direction that is perpendicular to a flow direction in which the cooling medium flows through the passage. One of the pin fins of each first group that is the located closest to a side surface of the base in the first group is a first outermost pin fin. The second groups of pin fins are located in the passage and adjacent to the heating element. The pin fins of each second group are arranged in the width direction that is perpendicular to the flow direction in which the cooling medium flows through the passage. One of the pin fins of each second group that is located closest to the side surface of the base in the second group is a second outermost pin fin. The second groups and the first groups are arranged alternately in the flow direction. The pin fins of the second groups and the first groups are provided in a staggered arrangement. The second outermost pin fin of each second group is more distant from the side surface of the base than the first outermost pin fin of each first group. Width between a side surface of the second outermost pin fin of each second group and the side surface of the base is the same as or larger than width between a side surface of the pin fin of each first group that is adjacent to the first outermost pin fin of the first group and the side surface of the second outermost pin fin.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is an exploded perspective view showing a cooling device according to an embodiment of the present invention;

FIG. 2 is a horizontal sectional view showing the cooling device of FIG. 1;

FIG. 3 is an enlarged fragmentary view showing the cooling device of FIG. 2;

FIG. 4 is a schematic view illustrating a cooling device of a comparative example;

FIG. 5 is a schematic view illustrating the cooling device of FIG. 1;

FIG. 6 is an enlarged fragmentary schematic view illustrating the cooling device of FIG. 1;

FIG. 7A is a fragmentary sectional view showing a cooling device according to a modification of the present invention; and

FIG. 7B is a fragmentary sectional view showing a cooling device according to another modification of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following will describe the cooling device according to the embodiment of the present invention with reference to FIGS. 1 through 6. Referring to FIG. 1, the cooling device is designated by reference numeral 10 and has a base 20. The base 20 includes a first base member 21 and a second base member 22 joined to each other. The members 21 and 22 are both made of aluminum and have substantially the same shape. Each of the members 21 and 22 has a rectangular outer plate 23, two sidewalls 25A that extend from the respective two short sides of the outer plate 23, two sidewalls 25B that extend from the respective two long sides of the outer plate 23, and a plate-like joint 26 that extends horizontally outward from the ends of the sidewalls 25A and 25B.

The base 20 has therein an inner space S that serves as a passage through which a cooling medium flows. A semiconductor device 28 that serves as a heating element is joined to the outer plate 23 of the first base member 21 via a rectangular insulating base plate 27 at the outer surface of the outer plate 23 whose inner surface faces the inner space S. More specifically, the insulating base plate 27 is joined at the lower surface thereof to the first base member 21 via a metal plate (not shown) that serves as a joining layer. It is noted that the long-side direction of the insulating base plate 27 corresponds to that of the first base member 21. The semiconductor device 28 is mounted on the upper surface of the insulating base plate 27 via a metal plate (not shown) that serves as a wiring layer.

A rectangular support plate 32 is interposed between the first base member 21 and the second base member 22 and supports a plurality of pin fins 31 in the inner space S of the base 20. The support plate 32 has substantially the same shape and size in planar view as the outer profile of the joints 26 of the first and second base members 21 and 22. The support plate 32 is held between the joints 26 of the base members 21 and 22 so that the opposite surfaces of the support plate 32 face the outer plates 23 of the base members 21 and 22, respectively. The joint 26 of the first base member 21, the joint 26 of the second base member 22 and the support plate 32 are sealingly joined together by brazing. The support plate 32 thus disposed in the cooling device separates the inner space S into a first passage S1 (FIG. 2) and a second passage S2 (FIG. 1).

The sidewalls 25A and the joint 26 of the first base member 21 have recesses 33A and 34A (refer to FIG. 2). The sidewalls 25A and the joint 26 of the second base member 22 have also recesses 33B and 34B. With the joints 26 of the first and second base members 21 and 22 joined in place to the support plate 32 on the opposite surfaces thereof, the recesses 33A and 34A of the first base member 21 allow the first passage S1 to communicate with the outside of the base 20. Similarly, the recesses 33B and 34B of the second base member 22 allow the second passage S2 to communicate with the outside of the base 20.

A cylindrical inlet tube 41 is connected to the base members 21 and 22 at the recesses 33A and 33B thereof so that cooling medium flows into the first and second passages S1 and S2 via the openings formed by the recesses 33A and 33B, respectively. In addition, a cylindrical outlet tube 42 is connected to the base members 21 and 22 at the recesses 34A and 34B thereof so that cooling medium flows out of the first and second passages S1 and S2 via the openings formed by the recesses 34A and 34B, respectively. Thus, the cooling medium flows from the inlet tube 41 toward the outlet tube 2 in the direction along the long side of the base members 21 and 22.

Referring to FIG. 2, the pin fins 31 are formed on both of the upper and lower surfaces of the support plate 32 in a staggered arrangement in planar view thereby to form pin fin units 50. The staggered arrangements of the pin fins 31 on the upper and lower surfaces of the support plate 32 are the same. Specifically, the pin fins 31 on each of the opposite surfaces of the support plate 32 in the illustrated embodiment (pin fins on one surface being shown in the drawing) include seven rows of pin fins 31, the rows being substantially equidistantly spaced in the direction along the long side of the support plate 21 (or in the flow direction in which the cooling medium flows through the inner space S). More specifically, the seven rows include three first rows of pin fins, each row including three first pin fins 31B arranged at a predetermined spaced interval in the direction along the short side of the support plate 32 and four second rows of pin fins, each row including four second pin fins 31A arranged at the same spaced interval in the same direction as the first pin fins 31B. Furthermore, the first rows of the first pin fins 31B and the second rows of the second pin fins 31A are arranged alternately in the flow direction and the first and second pin fins 31B and 31A of any two adjacent first and second rows are disposed in a staggered arrangement, as clearly shown in FIG. 2.

As shown in FIGS. 1 and 2, all the pin fins 31 are cylindrical in shape with the same length and diameter and extend from the respective surfaces of the support plate 32. All the pin fins 31 that extend upward from the upper surface of the support plate 32 are joined at the upper ends thereof to the outer plate 23 of the first base member 21. All the pin fins 31 that extend downward from the lower surface of the support plate 32 are joined at the lower ends thereof to the outer plate 23 of the second base member 22.

Each of the inner side surfaces of the sidewalls 25B of the base members 21 and 22 that extend along the flow direction of cooling medium are formed with three projections 60 projecting inward from the inner side surface and spaced at the same interval as the pin fins 31 in the flow direction, as shown in FIGS. 2 and 3. As seen in FIG. 2, each projection 60 has the shape of a segment of a circle that is the same as the circle of the cylindrical pin fin 31 in horizontal section of the base 20 (the segment of the circle is smaller than the semicircle). The projection 60 is formed so that the vertical section thereof is reduced gradually toward the end. The projection 60 is formed so that any normal to the outer circumferential surface of the projection 60 is directed inward of the inner space S of the base members 21 and 22 away from the sidewall 25B.

With the support plate 32 held between the joints 26 of the base members 21 and 22, the projections 60 and the first pin fins 31B are arranged along three parallel phantom lines extending in the direction along the short side of the support plate 32 (or in width direction perpendicular to the flow direction). In the present embodiment, the first pin fins 31B and the projections 60 that are arranged along three parallel phantom lines extending in the width direction form first groups of pin fins. In this case, the projections 60 that form part of the sidewalls 25B of the base members 21 and 22 will be regarded as the first outermost pin fins of the first groups of pin fins.

In the present embodiment, four rows of second pin fins 31A arranged along the width direction across the flow direction form second groups of pin fins. The second pin fins 31A that are located closest to the opposite sidewalls 25B of the base members 21 and 22 in each of the second groups of pin fins are regarded as the second outermost pin fins 31A1. Unlike the first outermost pin fins, the second outermost pin fins 31A1 are separated from the sidewalls 25B of the base members 21 and 22. In this respect, the projections 60 are closer to the side surfaces of the sidewalls 25B that extends along the flow direction of the cooling medium in the inner space S than the second outermost pin fins 31A1. That is, the second outermost pin fins 31A1 are more distant from the side surfaces of the sidewalls 25B than the projections 60.

It is noted that the distance L1 or the shortest distance between the outer circumferential surface (side surface) of the second outermost pin fin 31A1 and the inner side surface of the adjacent sidewall 25B of each of the base members 21 and 22 is larger than the distance L2 or the shortest distance between the outer circumferential surface (side surface) of the first pin fin 31B that is located closest to the projection 60 in the first group of pin fins and the outer circumferential surface (side surface) of its adjacent second outermost pin fin 31A1. Therefore, the width W1 between the outer circumferential surface of the second outermost pin fin 31A1 and the inner side surface of the adjacent sidewall 25B of each of the base members 21 and 22 is larger than the width W2 between the outer circumferential surface of the first pin fin 31B that is located closest to the projection 60 in the first group of pin fins and the outer circumferential surface (side surface) of its adjacent second outermost pin fin 31A1.

The distance L3 or the shortest distance between the outer circumferential surface of the projection 60 and the outer circumferential surface of its adjacent second outermost pin fin 31A1 is substantially the same as the distance L2. Therefore, the width W3 between the outer circumferential surface of the projection 60 and the outer circumferential surface of its adjacent second outermost pin fin 31A1 is substantially the same as the width W2.

The following will describe the operation of the above-described cooling device 10. Referring to FIG. 4 illustrating the manner in which the cooling medium flows in the cooling device of a comparative example that is designated by reference numeral 110, the cooling medium flows not only through the region P1 of the inner space S in which pin fins 131 are formed as indicated by solid arrows in FIG. 4, but part of the cooling medium flows through the region P2 of the inner space S between the outermost rows of pin fins 131 and the inner side surfaces of the base 120 as indicated by dashed-dotted arrows in FIG. 4. The cooling medium flowing through the region P2 contributes very little to heat radiation from the base 120 through the pin fins 131, so that efficient cooling of the semiconductor device 28 joined to the base 120 cannot be accomplished.

Referring to FIG. 5 illustrating the manner in which the cooling medium flows in the cooling device 10 of the present embodiment, on the other hand, the width W1 between the outer circumferential surface of the second outermost pin fin 31A1 and the inner side surface of its adjacent sidewall 25B in the cooling device 10 of the present embodiment is smaller than the width W11 between the sidewall 125B and the pin fin 131 adjacent to the sidewall 125B in the cooling device 110 of the comparative example shown in FIG. 4. Thus, the cooling medium steadily flows through the region P1 of the inner space S as indicated by solid arrows in FIG. 5. Therefore, the cooling medium efficiently contributes greatly to heat radiation from the base 20 through the pin fins 31 thereby to efficiently cool the semiconductor device 28 joined to the base 20.

The width W4 of the inner space S of the base 20 of the cooling device 10 in the present embodiment may be smaller than the width W14 of the inner space S of the base 120 of the cooling device 110. Therefore, the dimension of the base 20 in the width direction perpendicular to the flow direction of the cooling medium is reduced and hence the base 20 is made smaller.

In the present embodiment wherein the inner space S of the base 20 has the width W4, no passage of the cooling medium flowing through the inner space S of the base 20 has a width that is reduced compared to the width W2. Therefore, the pressure loss occurring when the cooling medium flows through the inner space S of the base 20 is prevented from being increased.

Referring to FIG. 6, the cooling medium flowing along the sidewall 25B of the base 20 is guided inward away from the sidewall 25B by the projection 60, as indicated by arrowed line. Therefore, the cooling medium is guided to flow toward the region P1 of the inner space S.

The width W3 is substantially the same as the width W2. In the present embodiment wherein the projection 60 is formed on the sidewall 25B of the base 20, no passage of the cooling medium flowing through the inner space S of the base 20 has a width that is reduced compared to the width W2. Therefore, the pressure loss occurring when the cooling medium flows through the inner space S of the base 20 is prevented from being increased.

The above-described embodiment has the following advantageous effects.

(1) In the present embodiment according to the present invention wherein the width W1 between the outer circumferential surface of the second outermost pin fin 31A1 and the inner side surface of its adjacent sidewall 25B of each of the base members 21 and 22 is larger than the width W2 between the outer circumferential surface of the first pin fin 31B adjacent to the projection 60 in the first group of pin fins and the outer circumferential surface of its adjacent second outermost pin fin 31A1, the sidewall 25B of the base members 21 and 22 is located close to the pin fins 31 while a sufficient space or distance for the width W1 between the second outermost pin fin 31A1 and its adjacent sidewall 25B of the base members 21 and 22 is ensured. Thus, the cooling medium can steadily flow through the region P1 of the inner space S and the pressure loss occurring when the cooling medium flows through the inner space S of the base 20 is prevented from being increased. Therefore, such smooth flow of the cooling medium through the region P1 of the inner space S helps to cool the semiconductor device 28 efficiently. In addition, in the present embodiment wherein the inner side surface of the base 20 is located close to the pin fins 31, the width dimension of the inner space S is reduced thereby to reduce the size of the base 20 having the inner space S and hence the size of the cooling device 10.

(2) The width W3 between the outer circumferential surface of the projection 60 and the outer circumferential surface of its adjacent second outermost pin fin 31A1 is substantially the same as the width W2 between the outer circumferential surface of the first pin fin 31B adjacent to the projection 60 in the first group of pin fins and the outer circumferential surface of its adjacent second outermost pin fin 31A1. In addition, the width W1 between the outer circumferential surface of the second outermost pin fin 31A1 and the inner side surface of its adjacent sidewall 25B of each of the base members 21 and 22 is larger than the width W3 between the outer circumferential surface of the projection 60 and the outer circumferential surface of its adjacent second outermost pin fin 31A1. Thus, the width W1 is larger than the width W2. Since a sufficient space or distance for the width W1 is ensured, the pressure loss occurring when the cooling medium flows through the inner space S of the base 20 is prevented from being increased.

(3) In the present embodiment, the projection 60 formed projecting into the inner space S from the sidewall 25B that extends along the flow direction of the cooling medium in the inner space S guides the cooling medium toward the region P1 of the inner space S, thereby to allow the cooling medium to flow further steadily through the region P1 of the inner space S.

(4) In the present embodiment wherein the projection 60 is formed so that the vertical section thereof is reduced gradually toward its end, even if the distance L3 is set relatively small, a sufficient space or distance for the width between the outer circumferential surface of the projection 60 and the outer circumferential surface of its adjacent second outermost pin fin 31A1 is ensured. Therefore, the pressure loss occurring when the cooling medium flows through the space between the projection 60 and its adjacent second outermost pin fin 31A1 is further reduced.

(5) The base 20 is reinforced by the pin fins 31 thereby to increase its rigidity. Therefore, the reinforced base 20 restricts warping of the base 20 occurring due to the difference in the linear thermal expansion coefficient between the insulating base plate 27 and the base 20.

The present embodiment may be practiced as exemplified below.

Referring to FIG. 7A, the projection 60 may be formed in the shape of a semicylinder having a semicircle of a circle that is the same as that of the cylindrical pin fin 31 in horizontal section of the base 20.

Referring to FIG. 7B, the projection 60 may be formed in the shape of a partial cylinder having a partial circle of a circle that is the same as that of the cylindrical pin fin 31 and being larger in horizontal section than the semicylinder of FIG. 7A.

In the above-described embodiment, it may be so configured that the width W1 between the outer circumferential surface of the second outermost pin fin 31A1 and the inner side surface of its adjacent sidewall 25B of each of the base members 21 and 22 is the same as the width W2 between the outer circumferential surface of the first pin fin 31B adjacent to the projection 60 in the first group of pin fins and the outer circumferential surface of its adjacent second outermost pin fin 31A1.

In the above-described embodiment, projections similar in shape to the projections 60 shown in FIGS. 6, 7A and 7B may be formed so as to extend from the opposite surfaces of the support plate 32.

In the above-described embodiment, the projections such as the projections 60 shown in FIGS. 6, 7A and 7B may have the shape of a partial cylinder having a partial circle of a circle having a diameter that is different from that of the cylindrical pin fin 31.

In the above-described embodiment, the projections 60 of FIGS. 6, 7A and 7B need not to be formed in a partial cylindrical shape. The projection 60 may be formed to have a spherical outer surface. In such a structure, the flow direction of the cooling medium passing through the space between the projection 60 and its adjacent pin fin 31 is changed to the direction that is normal to the spherical outer surface of the projection 60. Therefore, the cooling medium flowing in the inner space S of the base 20 is efficiently guided toward the region of the inner space S in which the pin fins 31 are formed.

In the above-described embodiment, the pin fin 31 may be replaced by a pin of a polygonal column shape such as triangular prism or quadrangular prism.

In the above-described embodiment, the pin fins 31 may be arranged in a grid pattern in a planar view.

In the above-described embodiment, the number of pin fins 31 supported by the support plate 32 may be changed as desired.

In the above-described embodiment, the support plate 32 may be modified so as to have the pin fins 31 only on one side thereof without separating the inner space S into the upper and lower spaces. 

What is claimed is:
 1. A cooling device to which a heating element is joinable, comprising: a base having a passage through which a cooling medium flows; a plurality of first groups of pin fins located in the passage and adjacent to the heating element, wherein the pin fins of each first group are arranged in a width direction that is perpendicular to a flow direction in which the cooling medium flows through the passage, wherein one of the pin fins of each first group that is located closest to a side surface of the base in the first group is a first outermost pin fin; and a plurality of second groups of pin fins located in the passage and adjacent to the heating element, wherein the pin fins of each second group are arranged in the width direction that is perpendicular to the flow direction in which the cooling medium flows through the passage, wherein one of the pin fins of each second group that is located closest to the side surface of the base in the second group is a second outermost pin fin, wherein the second groups and the first groups are arranged alternately in the flow direction, wherein the pin fins of the second groups and the first groups are provided in a staggered arrangement, wherein the second outermost pin fin of each second group is more distant from the side surface of the base than the first outermost pin fin of each first group, wherein width between a side surface of the second outermost pin fin of each second group and the side surface of the base is the same as or larger than width between a side surface of the pin fin of each first group that is adjacent to the first outermost pin fin of the first group and the side surface of the second outermost pin fin.
 2. The cooling device according to claim 1, wherein width between a side surface of the first outermost pin fin and the side surface of the second outermost pin fin is the same as the width between the side surface of the pin fin of each first group that is adjacent to the first outermost pin fin of the first group and the side surface of the second outermost pin fin.
 3. The cooling device according to claim 1, wherein the first outermost pin fin is a projection that is formed projecting from the side surface of the base.
 4. The cooling device according to claim 3, wherein the projection is formed so that a cross section thereof is reduced gradually toward an end thereof.
 5. The cooling device according to claim 1, wherein the heating element is a semiconductor device that is joined to the base via an insulating base plate. 